In this paper we report synthesis and application of functionalized multiwalled carbon nanotubes (CNTs) with titanium dioxide nanoparticles (TiO2), 9-(1,3-dithiolan-2-y1)-6,7-dihydroxy-3,3-dimethy1-3,4dihydrodibenzo[b,d]furan-1(2H)-one (benzofuran derivative (DDF)) and 1-buty1-3-methylimidazolium tetrafluoroborate (IL) as high sensitive sensors for simultaneous determination of isoproterenol (IP) and serotonin (5-HT) using glassy carbon electrode. The modified electrode was characterized by different methods including a scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS) and voltammetry. A pair of well-defined redox peaks of DDF was obtained at the modified glassy carbon electrode by direct electron transfer between the DDF and the electrode. Dramatically enhanced electrocatalytic activity was exemplified at the modified electrode, as an electrochemical sensor to study the electro oxidation of IP and 5-HT. The differential pulse voltammetry data showed that the obtained anodic peak currents were linearly dependent on the IP and 5-HT concentrations in the range of 0.1-1300.0 and 1.0-650.0 mu M, respectively. The applicability of the modified electrode was demonstrated by simultaneous determination of IP and 5-HT in human serum.(C) 2014 Elsevier Ltd. All rights reserved.